1. Field of the Invention
The present invention relates to a gear synchronizer for power transmissions, and more particularly, but not exclusively, to a gear synchronizer of the type which comprises a gear member rotatable on a transmission shaft, a hub member mounted on the transmission shaft for rotation therewith and being formed thereon with external splines, a spline piece provided on a hub portion of the gear member for rotation therewith and being formed at one side thereof with a frustoconical portion and thereon with external splines, a clutch sleeve encircling the hub member and having internal splines in continual engagement with the external splines of the hub member, the clutch sleeve being axially shiftable to be engaged at the internal splines thereof with the external splines of the spline piece, a synchronizer ring mounted on the frustoconical portion of the spline piece for frictional engagement therewith, and a plurality of circumferentially spaced strut keys assembled with the inner circumference of the clutch sleeve and loaded radially outwardly into engagement with the clutch sleeve to abut against and urge the synchronizer ring toward the spline piece in a shifting operation of the clutch sleeve.
2. Description of the Prior Art
In U.S. Pat. No. 4,413,715 issued on Nov. 8, 1983, there has been proposed such a gear synchronizer of the Borg-Warner type as described above, wherein the clutch sleeve is axially shifted by a manual shift lever connected thereto to abut the strut keys against the synchronizer ring and to urge them toward the spline piece for effecting frictional engagement between the synchronizer ring and the spline piece. In such shifting operation of the clutch sleeve, the manual shift lever is loaded by a reaction force applied thereto from the synchronizer ring through the clutch sleeve. In the gear synchronizer, it is desirable to provide a cam mechanism for effecting frictional engagement between the synchronizer ring and the spline piece in shifting operation of the clutch sleeve. The cam mechanism, however, is apt to cause slight frictional engagement between the synchronizer ring and the spline piece in a condition where the clutch sleeve is retained in a neutral position.